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VerificationAttribute Class

Defines the metadata attribute of a Web content accessibility rule. This class cannot be inherited.

System.Object
  System.Attribute
    System.Web.UI.VerificationAttribute

Namespace:  System.Web.UI
Assembly:  System.Web (in System.Web.dll)

[AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Property, AllowMultiple = true)]
public sealed class VerificationAttribute : Attribute

The VerificationAttribute type exposes the following members.

  NameDescription
Public methodVerificationAttribute(String, String, VerificationReportLevel, Int32, String)Initializes a new instance of the VerificationAttribute class with accessibility guideline, checkpoint, reporting level, checkpoint priority, and error message.
Public methodVerificationAttribute(String, String, VerificationReportLevel, Int32, String, VerificationRule, String)Initializes a new instance of the VerificationAttribute class with accessibility guideline, checkpoint, reporting level, checkpoint priority, error message, VerificationRule.value, and related conditional property.
Public methodVerificationAttribute(String, String, VerificationReportLevel, Int32, String, VerificationRule, String, VerificationConditionalOperator, String, String)Initializes a new instance of the VerificationAttribute class with accessibility guideline, checkpoint, reporting level, checkpoint priority, error message, VerificationRule.value, related conditional property, a related conditional property value, and a reference guideline URL.
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  NameDescription
Public propertyCheckpointGets the accessibility checkpoint reference in the specified Guideline property.
Public propertyConditionalPropertyGets the left side of a conditional expression used as part of the verification accessibility checkpoint.
Public propertyConditionalValueGets the right side of a conditional expression used as part of the verification accessibility checkpoint.
Public propertyGuidelineGets the guideline that used for accessibility checking.
Public propertyGuidelineUrlGets the URL the can be used to get more information on the accessibility guidelines given in the Guideline property.
Public propertyMessageGets a message string when the accessibility checkpoint verification rule is true.
Public propertyPriorityGets the priority of the accessibility checkpoint.
Public propertyTypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
Public propertyVerificationConditionalOperatorGets a VerificationConditionalOperator enumeration value indication how the accessibility checkpoint is verified.
Public propertyVerificationReportLevelGets a VerificationReportLevel enumeration value indicating how the accessibility checkpoint is used.
Public propertyVerificationRuleGets a VerificationRule enumeration value indicating how the accessibility checkpoint is used.
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  NameDescription
Public methodEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Public methodGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeWhen overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)
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An instance of the VerificationAttribute class defines a Web content accessibility rule that can be verified. For more information on Web Content Accessibility Guidelines, see the World Wide Web Consortium (W3C) Web site.

The minimal amount of information required to define an instance of a VerificationAttribute includes:

  • A guideline that the verification rule represents. The value specified in the constructor sets the Guideline property.

  • A checkpoint of the guideline. The value specified in the constructor sets the Checkpoint property.

  • A checkpoint priority. The value specified in the constructor sets the Priority property.

  • A VerificationReportLevel enumeration value that represents the reporting level that should be rule belongs to. The value specified in the constructor sets the VerificationReportLevel property.

  • A message that is reported when the verification rule is true. The value specified in the constructor sets the Message property.

Optional properties of the verification rule that can be specified when creating an instance:

  • A VerificationRule enumeration value that represents how the verification rule should be interpreted. The value specified in the constructor sets the VerificationRule property.

  • A VerificationConditionalOperator enumeration value that represents the operator in the conditional expression used to test the verification rule. The value specified in the constructor sets the VerificationConditionalOperator property.

  • An accessibility reference guideline URL. The value specified in the constructor sets the GuidelineUrl property.

  • A conditional value representing the right side of a conditional expression. The value specified in the constructor sets the ConditionalValue property.

  • A conditional property representing the left side of a conditional expression. The value specified in the constructor sets the ConditionalProperty property.

The VerificationAttribute metadata can be defined class, property, and indexer declarations.

For more information about using attributes, see Extending Metadata Using Attributes.

The following code example demonstrates using the VerificationAttribute class. In the verification metadata definition, the guidelines used are "WCAG," the Web Content Accessibility Guideline, and "ADA," Americans with Disabilities Act Guidelines. For more information, see the World Wide Web Consortium (W3C) Web site.

The checkpoints used are "1.1" and "1194.22(a)" for WCAG and ADA, respectively, checkpoints for ensuring that a text equivalent exists for non-text elements. The VerificationAttribute is applied to the ImageText property that represents the text equivalent of another property called ImageProperty. If the ImageText property is not set, the accessibility verification will return the message "The image is missing a text equivalent."

		[Verification("ADA", "1194.22(a)", 
			VerificationReportLevel.Error, 1,
			"The image is missing a text equivalent.", 
			VerificationRule.NotEmptyString, "ImageUrl"),
		Verification("WCAG", "1.1", 
			VerificationReportLevel.Error, 1, 
			"The image is missing an text equivalent.", 
			VerificationRule.NotEmptyString, "ImageUrl")]
		public virtual String ImageText
		{
			get
			{
				object obj = ViewState["ImageText"];
				return ((obj == null) ? String.Empty : (string)obj);
			}
			set
			{
				ViewState["ImageText"] = value;
			}
		}
		public virtual String ImageUrl
		{
			get 
			{
				object obj = ViewState["ImageUrl"];
				return ((obj == null) ? String.Empty : (string)obj);
			}
			set 
			{ 
				ViewState["ImageUrl"] = value;
			}
		}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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